The present invention relates to a magnetic disk drive for use in a data processing apparatus or similar apparatus and, more particularly, to a magnetic disk drive capable of reducing the distortions of magnetic disks, i.e., warping in the radial direction and waving in the circumferential direction occurring when the disks are stacked and clamped.
A conventional magnetic disk drive has a spindle motor rotatable at high speed. A plurality of magnetic media in the form of disks are stacked on the spindle motor. The adjoining disks are spaced a predetermined distance from each other by a spacer ring on the spindle motor. A top spacer is mounted on the top of the stack of alternating disks and spacer rings in order to reduce: the deformation of the disks in the circumferential direction. A clamp ring is made of an elastic material and fastened to the upper end of the spindle motor via the top spacer by screws. When the clamp ring is fastened to the spindle motor, it clamps the disks, spacer rings and top spacer to the spindle motor due to the elastic deformation thereof. The spindle motor and clamp ring press the disks and spacer rings over the same diameter as each other. If the spindle motor and clamp ring press the disks and spacer rings at different positions from each other, the disks and spacer rings will deform, or warp, in the radial direction of the disks.
The top spacer and clamp ring of the conventional disk drive suffer from a lack of rigidity since they are made of aluminum and since the thickness thereof is limited in order to reduce the overall thickness of the disk drive. Specifically, when the clamp ring is fastened to the spindle motor, the clamp ring itself deforms to, in turn, cause the top spacer to deform. As a result, the disks themselves deform, following the deformation of the top spacer. Then, magnetic heads included in the disk drive cannot follow such deformation of the disks and, therefore, fail to write or read data in or out of the disks accurately. Moreover, the heads are apt to crash against the deformed disks.
Japanese Patent Laid-Open Publication No. 4-337558, for example, discloses a magnetic disk drive of the type described.